In rubber products such as belts of radial tires, body plys for carcasses, various industrial belt members, an article prepared by coating a steel wire subjected to brass plating or a steel cord prepared by twisting plural wirers of the above steel wire with a rubber has so far been used to thereby obtain a reinforcing effect thereof. In this case, an adhesive property between the steel cord and the rubber has to be sufficiently secured in order to sufficiently exert the reinforcing effect. From the above viewpoint, a proportion of copper to zinc in brass plating, optimizing a plating thickness and the like are studied, and a certain amount of knowledges has so far been obtained.
In general, a performance required in adhesion of a brass-plated steel cord with a coating rubber does not only demand that an initial adhesive property is good, but various conditions that there are no troubles which originate in deterioration of an adhered interface when rubber products such as tires are exposed to deterioration environment in an actual use and that troubles in a production step of rubber products such as tires are prevented and the compounding cost is kept down have to be satisfied.
Accordingly, the present inventors have proposed a steel wire and a steel cord which are excellent in an adhesive property with rubbers, such as a steel wire for reinforcing rubber products which is provided with a brass-plated layer on a peripheral surface of the wire and in which a content of phosphorus contained in the form of oxide in a wire surface layer region extending from a surface of the brass-plated layer up to a depth of 5 nm in a wire radial direction toward the inside is controlled to 1.5 atomic % or less and a steel cord prepared by twisting plural wires of the above wire (refer to, for example, patent document 1), and further the present inventors have proposed a rubber-steel cord composite comprising a rubber composition which contains 0.1 to 5 parts by weight of a maleimide resin and 0.5 to 8 parts by weight of a bisphenol compound having two tert-butyl groups based on a rubber component containing 50% by weight or more of natural rubber and which is compounded with at least one kind of higher fatty acid and a single wire of a steel wire which has a brass-plated layer on a peripheral surface thereof and in which a content of phosphorus contained in the form of oxide in a wire surface layer region extending from a surface of brass-plated layer up to a depth of 5 nm in a wire radial direction toward the inside is 1.5 atomic % or less or a steel cord prepared by twisting plural wires of the above steel wire (refer to, for example, patent document 2).
The rubber-steel cord composites described in patent documents 1 and 2 can exert the excellent adhesive property than ever before, but the existing situation is that a rubber-steel cord composite which provides better workability and is excellent in an adhesive property between a rubber and a steel cord is eagerly desired to be developed.
On the other hand, high elasticity, low heat build-up, deterioration resistance, an adhesive property and the like are required of rubber compositions such as coating rubbers which are reinforced by a steel cord, and in order to allow the above rubber-steel cord composites to exert particularly a high reinforcing effect and obtain reliability, adhesion which is stable and changed less with the passage of time is required in the rubber-steel cord composites.
Also, when rubber is adhered to metal such as a steel wire, a method in which rubber and metal are bonded at the same time as vulcanization, that is, a direct vulcanization bonding method is known, and in this case, it is considered to be effective in carrying out vulcanization of rubber and bonding of rubber and metal at the same time to use a sulfeneamide base vulcanization accelerator which provides vulcanization reaction with a delayed action.
For example, N,N-dicyclohexyl-2-benzothiazolylsulfeneamide (hereinafter abbreviated as “DCBS”) represented by the following formula is known as a vulcanization accelerator which provides vulcanization reaction with the largest delayed action among sulfeneamide base vulcanization accelerators which are commercially available at present:

Also, when a larger delayed action than that of DCBS is required, a vulcanization retardant other than sulfeneamide base vulcanization accelerator is used in combination. N-(cyclohexylthio)phthalimide (hereinafter abbreviated as “CTP”) is known as a commercially available representative vulcanization retardant. However, it has been already known that if this CTP is compounded with rubber in a large amount, that exerts an adverse effect on the physical properties of the vulcanized rubber and causes blooming which deteriorates the appearance of the vulcanized rubber and exerts an adverse effect on an adhesive property thereof.
Further, known as sulfeneamide base vulcanization accelerators other than DCBS described above are, for example, bissulfeneamide represented by a specific formula (refer to, for example, patent document 3) and a benzothiazolylsulfeneamide base vulcanization accelerator in which an amine originating in natural oils & fats is used as a raw material (refer to, for example, patent document 4).
However, with respect to the sulfeneamide base vulcanization accelerators described in patent documents 3 and 4, only the rubber physical properties thereof are described, and the adhesion performances are neither described nor suggested. In addition thereto, it is neither described nor suggested at all that the sulfeneamide compound of the present invention can be used as a novel vulcanization accelerator for rubbers.
Further, several production processes for the sulfeneamide compound used in the present invention are known in, for example, patent documents 5, 6 and 7, but capability of using these compounds as a novel vulcanization accelerator for rubbers and an adhesion performance with a steel cord which is exerted by the above accelerators are neither described nor suggested therein at all.